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31.
Bikash Sinha 《Pramana》1989,32(4):523-539
The general characteristics of the transition from hadronic matter of nucleons, three quark bags, mesons of quark antiquark
pairs to quark gluon plasma is discussed. The phenomenological approach essentially guided by the MIT bag model and general
thermodynamic criteria of first-order phase transition is elaborated. The more realistic calculations using the QCD lattice
renormalization quark are touched upon. Possible signals of quark-gluon plasma are discussed. The central issue of deciphering
plasma signals from the signals of hot hadronic matter is discussed in detail.
The signals of the quark-gluon plasma, a subject of considerable interest in contemporary literature are focussed only on
(i) dileptons (ii) photon photon pairs and (iii)J/Ψ suppression (with special emphasis on CERN experiments). The lingering shadow of “EMC” effect is also mentioned.
Relics of the very early universe microseconds after the big bang in today’s universe (∼ 15 billion years later) are discussed.
Finally, the outlook of this very exciting field is presented, a purely personal viewpoint, generalized eventually to poetic
signals of the creation of the universe. 相似文献
32.
The concerned azooximes (L1OH, 1) are of type p-X-C6H4C(N2Ph)(NOH) (X = H, Me, Cl). The reaction of [Re(MeCN)Cl3(PPh3)2] with [Ag(L1OH)(L1O)] in cold dichloromethane-acetonitrile solvent has furnished the green colored ionized azoimine complex [ReV(O)Cl(PPh3)2(L1)](PF6), 2. In effect L1O- has undergone oxidative addition, the oxygen atom being transferred to the metal site. Upon treatment of [ReV(NPh)Cl3(PPh3)2] with L1OH in solution, the neutral azoimine complex [ReV(NPh)Cl3(L1H)], 3, resulted due to the spontaneous transfer of the oxime oxygen atom to a PPh3 ligand, which is eliminated as OPPh3. In contrast, the oxime of 2-acetylpyridine (L2OH, 4) did not undergo oxygen atom transfer and simply afforded the imine-oxime complex [ReV(NC6H4Y)Cl2(PPh3)(L2O)], 5, upon reacting with [ReV(NC6H4Y)Cl3(PPh3)2] (Y = H, Me, Cl). The spectral and electrochemical properties of 2, 3, and 5 and the structures of three representative compounds are reported. In the cation of 2 (X = H) the two PPh3 ligands lie trans to each other and the equatorial plane is defined by the five-membered azoimine chelate ring and the oxo and chloro ligands. The oxo ligand which forms a model triple bond (Re-O length 1.616(6) A) lies cis to the imine-N atom. In 3 (X = Cl) the ReCl3 fragment has meridional geometry and the imido nitrogen lies trans to the imine nitrogen of the planar azoimine chelate ring. In 5 x H2O (Y = Me), the Cl, oximato-N, and P atoms define an equatorial plane and the pyridine-N lies trans to the imido-N. The water of crystallization is hydrogen bonded to the oximato oxygen atom (O...O, 2.829(5) A). Reaction models in which chelation of the azooxime precedes oxygen atom transfer are proposed on the basis of oxophilicity of trivalent rhenium, Lewis acid activity of pentavalent rhenium, electron withdrawal by the azo group, and observed relative disposition of ligands in products. 相似文献
33.
Reacting Re(CO)5Cl with the azopyridine ligand (1) (L) in boiling benzene afford the complex Re(CO)3Cl(L), (2) in excellent yield [L=2-(p-Cl-C6H4NN)C5H4N]. The chelation of the azopyridine ligand accompanied by displacement of the two carbon monoxide ligands furnish a five-membered chelate ring. Structure determination of complex (2) has revealed a distorted octahedral ReC3N2Cl coordination sphere. The Re–N(pyridine) and, Re–N(azo) distances are 2.158(3) and 2.153(6) Å respectively, and the N–N length [1.273(4) Å], implicate relatively weak Re-azo(π*) back–bonding. The Re(CO)3Cl(L) lattice consists of C–H...Cl hydrogen bonding and Cl...O non-bonded interactions constituting a supramolecular network. Extended Hückel calculations reveal that the LUMO of Re(CO)3Cl(L) is Ca. 57% azo in character. One-electron quasireversible electrochemical reduction of the complex occurs near −0.3 V versus Saturated Calomel electrode(s.c.e.) The redox orbital is believed to belong to the above noted LUMO. Electrogenerated Re(CO)3Cl(L•–) underwent spontaneous solvolytic chloride displacement in MeCN, resulting in the isolation of Re(CO)3(MeCN)(L•–). The latter complex in turn reacted with imidazole and triphenylphosphine, furnishing Re(CO)3(C3H4N2)(L•–) and Re(CO)3(PPh3)(L•–), respectively. The pattern of carbonyl stretching frequencies of these radical anion complexes is similar to that of Re(CO)3Cl(L) but with shifts to lower frequencies by 10–20 cm−1. All three radical anion systems are one-electron paramagnetic (1.7–1.8 μB). The unpaired electron is primarily localized on the azoheterocycle ligand in a predominantly azo-π* orbital, but a small metal contribution (185, 187Re, I=5/2) is also present. Thus Re(CO)3(MeCN)(L•–) and Re(CO)3(C3H4N2)(L•–) display six-line e.p.r. spectra (A ˜ 28 G). The line shapes and intensities are characteristic of the presence of g-strain. In the case of Re(CO)3(PPh3)(L•–) seven nearly equispaced lines are observed due to virtually equal coupling between the metal and 31P (I=&frac;) nuclei. The g-values of the radical species are slightly higher than the free-electron value of 2.0023. 相似文献
34.
35.
Bikash K. Panda 《Transition Metal Chemistry》2005,30(4):488-495
By reacting [Ru(RL1)(PPh3)2(CO)Cl], (1) (R = C6H4Me, Et) with an excess of CNBut in the presence of NH4PF6, organometallics of the type [Ru(RL2)(PPh3)2(CNBut)2]PF6, (2) have been isolated in excellent yield [RL1 = C6H2O-2-CHNHR(p)-3-Me-5, RL2 = C6H2(CO)-O-2-CHNHR(p)-3-Me-5]. These organometallics, on controlled hydrolysis, produce [Ru(L3)(PPh3)2(CNBut)2], (3) in very good yield (L3 = C6H2(CO)-O-CHO-3-Me-5). In both ([2(C6H4Me)] · 2H2O) and ([3] · 2CH2Cl2) the two phosphine ligands lie in trans positions. In ([2(C6H4Me)] · 2H2O) the Ru(C6H4MeL2) fragment, excluding the pendant tolyl ring, is a near perfect plane (mean dev ~ 0.02Å) which makes a dihedral angle of 5.2° with the tolyl plane. The acyl chelate ring in ([2(C6H4Me)] · 2H2O) is excellently planar with a mean deviation of 0.006°. In ([3] · 2CH2Cl2) the Ru(L3) fragment defines a crystallographic plane of symmetry, the coordinates of the atom being of the type x, 1/4z. The complex ([2C6H4Me)] · 2H2O) displays N–HȮFO (iminium-phenolato) hydrogen bonding while in ([3] · 2CH2Cl2) C–H...O hydrogen bonding is present. Characteristic spectral data (u.v.–vis, i.r. and 1H n.m.r.) of the complexes are reported. A notable feature is that an allowed band near 500 nm due to the t2g → π*(azomethine) charge transfer transition, which is diagnostic of the coordinated iminium-phenolato function, is present in (3) but this band is absent in the aldehydic acyl complex (2). In the 1H n.m.r. spectrum the N+–H signal in (2) (near 13.5 ppm) is split into a doublet due to transcoupling with the azomethine proton. The aldehydic proton of (3) resonates as a sharp singlet near 10 ppm. In CH2Cl2 solution (2) and (3) display quasireversible a RuIII/RuIIcyclic voltammetric response with E1/2 near 0.9 and 0.5 V versuss.c.e. The conversion (2) → (3) is accompanied by the nucleophilic attack of water. The complex (3) is also obtained directly from (1) by reaction with CNBut in the presence of H2O. The aldehyde function in (3) is deactivated by the existing acyl moiety; as a result further decarbonylation does not take place. 相似文献
36.
Real time band selective F1‐decoupled proton NMR for the demixing of overlay spectra of chiral molecules 下载免费PDF全文
Nilamoni Nath Ajay Verma Bikash Baishya Chunni Lal Khetrapal 《Magnetic resonance in chemistry : MRC》2017,55(6):553-558
The small chemical shift dispersion and complex multiplicity pattern in proton NMR limit quantifications, for instance the determination of enantiomeric excess (ee) for an enantiomeric mixture. Herein, we present a simple proton–proton correlation experiment with band selective homonuclear (BASH) decoupling in both F1 and F2 dimensions, for the removal of scalar and residual dipolar couplings to provide collapsed singlet for each chemical site. The method has been demonstrated to separate the severely overlapped spectra of enantiomers using both chiral isotropic and anisotropic phases as well as a small biomolecule, particularly for the diastereotopic protons and also for the determination of ee. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
37.
Bikash Karmakar 《Tetrahedron letters》2010,51(20):2748-2750
An efficient, mild and environmentally friendly method has been developed for the Strecker reaction to synthesize α-aminonitriles in the presence of K2PdCl4 as a catalyst. The three-component one-pot condensation of an aldehyde, amine and trimethylsilyl cyanide proceeded smoothly in water to afford the corresponding product in high yield with short reaction times. 相似文献
38.
Bikash Sinha 《Nuclear Physics A》1973,203(3):473-480
The second-order nucleon-nucleus optical potential has been calculated by using a simple second-order perturbation formalism. The results obtained by using an effective energy denominator indicate that the closure approximation is not valid for scattering. 相似文献
39.
Mrinal Samanta Banikalyan Swain Madhubanti Basu Girishbala Mahapatra Bikash R. Sahoo Mahismita Paichha Saswati S. Lenka Pallipuram Jayasankar 《Applied biochemistry and biotechnology》2014,174(1):309-327
Toll-like receptors (TLRs) are a class of innate immune receptors that sense pathogens or their molecular signatures and activate signaling cascades to induce a quick and non-specific immune response in the host. Among various types of TLRs, TLR22 is exclusively present in teleosts and amphibians and is expected to play the distinctive role in innate immunity. This report describes molecular cloning, three-dimensional (3D) modeling, and expression analysis of TLR22 in rohu (Labeo rohita), the most commercially important freshwater fish species in the Indian subcontinent. The open reading frame (ORF) of rohu TLR22 (LrTLR22) comprised of 2,838 nucleotides (nt), encoding 946 amino acid (aa) residues with the molecular mass of ~107.6 kDa. The secondary structure of deduced LrTLR22 exhibited the presence of signal peptide (1–22 aa), 18 leucine-rich repeat (LRR) regions (79–736 aa), and TIR domain (792–935 aa). The 3D model of LrTLR22-LRR regions together elucidated the horse-shoe-shaped structure having parallel β-strands at the concave surface and few α-helices at the convex surface. The TIR domain structure revealed alternate presence of five α-helices and β-sheets. Phylogenetically, LrTLR22 was closely related to common carp and exhibited significant similarity (92.2 %) and identity (86.1 %) in their amino acids. In rohu, TLR22 was constitutively expressed in all embryonic developmental stages, and tissue-specific analysis illustrated its expression in all examined tissues, highest was in liver and lowest in brain. In vivo modulation of TLR22 gene expression was analyzed by quantitative real-time PCR (qRT-PCR) assay following stimulation with lipopolysaccharide (LPS), synthetic double stranded RNA (polyinosinic-polycytidylic acid), and bacterial (Aeromonas hydrophila) RNA. Among these ligands, bacterial RNA most significantly (p?0.05) induced TLR22 gene expression in most of the tested tissues. In A. hydrophila infection, induction of TLR22 gene expression was also observed in majority of the tested tissues. Together, these data suggested that in addition to sensing other microbial signatures, TLR22 can recognize bacterial RNA and may play the important role in augmenting innate immunity in fish. 相似文献
40.
The temperature and the normal components of stress and displacement around an external circular crack in an infinite transversely
isotropic body have been calculated in the present paper. The stress intensity factor has been found and a comparison of the
results with those for the isotropic case has been presented graphically. 相似文献